It is alarming that an account of a high-school massacre is at the centre of Douglas Coupland's latest novel. Once such things begin to register in the laconic worldview of the prophet of Generation X, it suggests that school shootings can be added to strip-malls, McJobs and semi-disposable flat-pack furniture as just another banal feature of the north American landscape.

Coupland's most recent novels have been vehicles for his increasingly morbid obsessions. Miss Wyoming expounded his fascination with air disasters. All Families Are Psychotic contained a bizarre plot featuring a farewell letter placed by Prince William in his mother's coffin. Hey Nostradamus! was inspired by a news report about the massacre at Columbine High School, Colorado, in April 1999, when two teenage gunmen slaughtered a teacher and 14 of their fellow students.

Coupland has already re-created that scenario in an art installation entitled "Tropical Birds" - a reference to the chorus of mobile ring-tones emerging from a pile of bloodstained backpacks. That image reappears in the opening chapter of the novel, transplanted to a fictional college in the author's hometown of Vancouver. But what is really shocking is not so much the savagery of the action as the restraint with which Coupland describes it. Hey Nostradamus! seems to signal a major shift in Coupland's style. He has toned down all the arch, ironic posturing and compulsive slew of pop-cultural references, allowing a newly meditative, moral tone to emerge. It is as if someone who usually slouches around in combat pants suddenly strides into the room wearing a suit.

This could, of course, be down to the fact that Coupland is growing older. There are many for whom the publication of Generation X ranks alongside the suicide of Kurt Cobain as the defining cultural moment of the early 1990s. But whereas Cobain made his statement and left, Coupland still has to negotiate the tricky transition into early middle age. He at least appears to have shaken his head free from the hysterical fuzz which afflicted his last two novels, enabling him to perceive the world with an altogether heightened sense of clarity and perspective. In the words of the book's first narrator, Cheryl, it becomes possible "to discuss the killings with the detachment I have from being in this new place".

The whereabouts of the "new place" Cheryl finds herself in is teasingly ambiguous as, technically, she is dead - the final victim of the gunmen's rampage. But from her nebulous location between this world and the next, Cheryl's thoughts drift between recollections of how she and her 17-year-old boyfriend secretly married in a Las Vegas ceremony, alongside a harrowing, slow-motion account of the massacre. We are remorselessly guided through events, interpreted by the victims as a firecracker prank, until the first victim's head lands on a bench "like a bag of gym equipment", the fire alarm and sprinkler systems are tripped into action and, finally, Jason (a second narrator) storms recklessly on to the scene to disarm and slay the ringleader.

Coupland's most recent novel, All Families Are Psychotic, was a disorientating cacophony of conflicting voices and ricocheting sub-plots, but here he calmly pares the story down to four separate narrators. As Cheryl's body cools in her husband's arms, "like dinner on a plate", the narrative is taken over by Jason, who reveals that 10 years after the tragedy he is still struggling to cope. The third section concerns Jason's mysterious disappearance, and is related by Heather, the woman who loves him and attempts to nurse him out of his trauma. The concluding section belongs to Jason's father, Reg, a granite-hard religious fanatic who tortures his family with his twisted strain of spiritual sadism.

Coupland's novel mounts a sustained assault on religious intolerance and the kind of glassy-eyed bigots who look forward to the afterlife like a trip to Disneyland. Reg's nadir is reached when he denounces his son as a murderer for killing one of the gunmen (potentially saving hundreds of lives). At this point, his character seems completely beyond redemption and, as a younger writer, Coupland would have been content simply to stoke our loathing for the man. But it is a measure of his new-found objectivity that he grants Reg the final word. The masterful concluding section of the book presents a pitiful portrait of a wretched, broken figure who has come to realise that he terrorised others as a means of extinguishing the terror within himself.

Hey Nostradamus! is Coupland's first novel to feature a full complement of three-dimensional characters rather than a swarm of exaggerated cartoons. He seems to have reached a new plane of philosophical awareness. When Jason goes missing, his girlfriend reports that it is "as if a door had opened up" to reveal what the suicidal impulse feels like. She goes on to reflect that there may be people "who are born with that little door open, and have to go through life knowing that they might jump through it at any moment". Somewhere deep in Coupland's consciousness is a little door marked "greatness". He may slip through it yet.